Comment on xkcd #3211: Amperage

brygphilomena@lemmy.dbzer0.com ⁨3⁩ ⁨days⁩ ago

• CADmonkey@lemmy.world ⁨3⁩ ⁨days⁩ ago

  Maybe it’s styropyro’s house?

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• Nollij@sopuli.xyz ⁨3⁩ ⁨days⁩ ago

  In the US, most protection comes from the breaker. It’s not common (or at least, not standard) to have overcurrent protection on extension cords, power strips, or even the outlet itself. And for typical wiring and uses, it usually works well enough. But it is possible to connect a space heater or hairdryer (1500w and 1800w respectively, due to the 80% rule for continuous draw) to that standard 16-gauge extension cord, or connect multiple space heaters to one circuit. Some homes are wired… Creatively… Making it easy to do. In these cases, you’re relying on the 15-amp breaker to trip, which would happen quickly. Not quite as quick, but still happens on a 20-amp. But it might melt a 15-amp receptacle first

  If it’s a 30-amp circuit, it won’t trip at all, unless the outlet melts to a short. And this is all assuming the wiring in the wall is rated for that amperage, which is implied but not stated. There are certainly a number of stories where someone upgraded the breaker to keep it from tripping, but didn’t upgrade the wiring.

  If we assume he’s talking about the wiring in the wall, this gets very simple. I once lived in a place where the upstairs bedroom and downstairs living room were on the same circuit. I currently live somewhere where a single circuit controls ALL of the bathroom outlets (multiple bathrooms), the garage, as well as outside outlets. Apparently GFCI outlets were more expensive than the entire mess of running copper all over the place.

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• Aermis@lemmy.world ⁨3⁩ ⁨days⁩ ago

  Well for starters most residential outlets are rated for 15 amps. You don’t need to run a lot of stuff on that outlet, a vacuum and a space heater is most likely enough for the outlet to overheat. Toss in an extension cord and another appliance and the outlet is going to melt. And since you’re only pulling like 25 amps once the short happens when the live parts touch each other the arc explosion would be spectacular. Since you’re on a 500 amp switch gear breaker with selective coordination set in a way that not only is the outlet done, but the wiring I’m assuming is not ran to the outlet in 600kcm copper, so all the wiring from the outlet to the breaker is also going up in vapor. By the time the breaker trips your house just went through a neat fireworks show and it’s ablaze.

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• bort@sopuli.xyz ⁨3⁩ ⁨days⁩ ago

  what’s he running that’s goong to melt those wires?

  500A on a 110V (220V?) main is a lot of W.

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  • brygphilomena@lemmy.dbzer0.com ⁨3⁩ ⁨days⁩ ago

    Yea, but what device draws that much power. In the us, most space heaters are 1200w, so about 10 amps. So he’d need to really have a high load device. You might be able to find some 30amp single phase loads.

    Putting them all on their own circuit does so much to actually protect him unless he has various extension cords or those 2 receptacle to 6 receptacle devices.

    For 500 amps, he should be running 1000 gauge wire. Which would be so impressive to run since each leg would be almost an inch and a half thick and $50 a foot. Each breaker would be over $2k, if he went with the cheapest 500amp breaker.

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